SIMPACKNews

Video Representation of Relative Motion
Example of Relative Motion: Relative Rolling
per formance of the overall system
sufficiently. This conventional model,
describing only the rigid body motion,
is to be enhanced by the introduction
of additional degrees of freedom to
allow relative motion as well.
Teamwork by Co-Simulation
Each of the models has it’s ad vantage,
MATLAB allows easy preprocessing of
flight test data and offers mathematical
libraries for various engineering problems,
and SIMPACK features powerful
solvers especially for kinematic tasks
and convenient 3D-vi suali sation.
The Co-Simulation Interface COSI offers
the opportunity to retain all these
advantages and merge the two simulation
tools. SIMULINK first computes
the aerodynamic forces and moments
resulting from control inputs and the
initial states. This information is passed
over to SIMPACK, which simulates the
kinematic behavior and re turns the appropriate
states back to SIMULINK.
Parameter Estimation
After the overall-model has been set
up it’s necessary to tune the model parameters.
Since a real system, equipped
with various sensors, is simulated, it is
possible to compare computed and
mea sured states. Tuning of the parameters
should result in a least possible
difference between data from measurement
and simu lation.
The estimation of the parameters is
done automatically with the help of an
output-error-method (FITLAB) which is
implemented under MATLAB by DLR
Braun schweig.
Fields of application
Having assembled and tuned the
simulation environment, it is finally
ready for utilisation. One practical use
of this model is to find correction terms
for flight data measurements. Understanding
the relative motion allows to
trans form measurements taken from
the capsule in corresponding values
of the parafoil. Another appli cation is
performing simulation studies to find
out whether rela tive motion has to be
considered for the design of the flight
con troller or not.
SIMPACK and SIMULINK make a perfect
team to simulate flight mechanics plus
kinematics. This combination is suitable
for more than the analysis of parafoil.
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